The specific aims of the proposed research are: 1. Pre-model development analysis: An experiment will be conducted to collect extensive lifting performance data to validate the displacement-time relationships developed by Slote and Stone (1963). The appropriate set of displacement-time curves will be used to drive the model developed in next phase. 2. Model development: An optimization model for lifting motion will be developed which explicitly considers the minimization of the sum of the squares of the active state of the musculoskeletal system alone with the minimization of the rate of the change of acceleration. Three distinct analytical approaches to this research goal will be explored. In each approach, both the kinematics and kinetics as functions of lifting trajectories segment configurations, and joint mobilities will be determined 3. Model validation and model application: The models developed will be validated by comparing the predicted kinematics to the experimental data derived in a second laboratory effort. Validated models can then be used to compare the use of stoop and squat lift. The proposed optimal programming model will be used for the design and evaluation of lifting tasks. This research will make a substantial contribution to the understanding of body motion by providing a tool with which the ergonomist can evaluate the worker and the task a priori, for the determination of preferred lifting methods and potentially stressful and hazardous conditions.